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Magnetics, IEEE Transactions on

Issue 4 • Date December 1974

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Displaying Results 1 - 25 of 32
  • [Front cover and table of contents]

    Publication Year: 1974 , Page(s): 0
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    Freely Available from IEEE
  • The 6th International Colloquium on Magnetic thin films--Minsk, USSR, August 29-31, 1973

    Publication Year: 1974 , Page(s): 1022 - 1023
    Cited by:  Papers (1)
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  • Pulse switching in thin magnetic films

    Publication Year: 1974 , Page(s): 1023 - 1027
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    The main results of the investigations of pulse switching in thin magnetic films with uniaxial anisotropy which have been obtained in Moscow State University are reviewed. Simultaneous investigation of integral switching properties, inner effective field, and dynamic domains produced during pulse switching has increased our understanding of bi-directional incoherent rotation mechanism and found new peculiarities of the pulse switching by domain boundary propagation. A new variety of incoherent rotation which manifests itself at strong fields has been found. It has been also found that the curve representing the pulse field dependence of an inverse switching time in the general case consists of five distinct regions. The relation between these regions and the switching mechanisms are discussed. View full abstract»

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  • Band model approach for the magnetic stiffness within ferromagnetic thin films

    Publication Year: 1974 , Page(s): 1028 - 1032
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    The magnetic stiffness within ferromagnetic thin films, considered as a tendency of the film to be homogeneous with respect to the distribution of magnetization directions, is defined on the basis of the domain structure as well as of the spin wave theory. The transversal stiffness parameter in thin films is calculated by means of the band model approach within a Hartree-Fock type of approximation. This parameter depends on the film thickness and, what is particularly interesting, on the surface effects. View full abstract»

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  • Some magnetooptical and HF properties of magnetic films

    Publication Year: 1974 , Page(s): 1033 - 1038
    Cited by:  Patents (5)
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    Several effects accompanying the propagation of electromagnetic waves through magneto-ordered media are discussed. First the information writing obtained by cooling through the Néel point of the antiferromagnetic substrate coupled by exchange interaction with the magnetic film is considered. By changing the exchange coupling it is possible to write and steadily retain arbitrary microdomain configurations. Peculiarities of magnetooptic effects were predicted by us and discovered in magnetically gyrotropic media with preset space distribution of magnetization. At the end, data on the photomagnetic effect in film of Mg-Mn ferrite are discussed. View full abstract»

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  • Long wavelength AC bias recording theory

    Publication Year: 1974 , Page(s): 1039 - 1048
    Cited by:  Papers (18)  |  Patents (4)
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    Long wavelength ac bias record sensitivity is computed utilizing a model in which both longitudinal and vertical record fields are considered. It is assumed that the recorded magnetization is related by an anhysteretic susceptibility tensor to the signal field. At each depth in the tape the signal field is evaluated where the bias field amplitude is equal to the tape coercivity. Neither the effects of demagnetizing fields nor spreads in particle switching fields are included. The calculation yields excellent quantitative agreement with experimental sensitivity and correlates well with the shape of measured sensitivity vs. bias curves. The predictions of this model are compared in detail with those calculated utilizing solely longitudinal fields. View full abstract»

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  • Motion reversal invariance in tape recorders

    Publication Year: 1974 , Page(s): 1048 - 1049
    Cited by:  Papers (1)
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    Under certain circumstances, when replaying prerecorded tapes, a reversal of head-tape motion causes a simple time reversal of the output. The occurrence of this phenomenon depends entirely upon the characteristics of the reproduce channel. Motion reversal invariance occurs when the time dependent part of the reproduce channel impulse response displays either of two types of symmetry;in the frequency domain this is equivalent to a quasi-linear phase response. View full abstract»

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  • Magnetostriction in some magnetic oxide compacted powders

    Publication Year: 1974 , Page(s): 1050 - 1052
    Cited by:  Papers (8)
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    Magnetostriction measurements have been made on a series of compacted powder samples of oxide pigments used in magnetic recording, to provide information for the evaluation of the role of magnetostriction in the recording process. Two composition series were measured at 294 K: one from γFe2O3through a range of partial reductions to Fe3O4, and another from 0 to 4 at. % Co in γFe2O3; also samples of CrO2. In addition, a 2 at. % Co-doped Fe3O4powder was measured as a function of field and temperature from 77 to 300 K. Magnetostriction was measured using a semiconductor strain gage on a rotating sample, in fields up to 9 kOe. View full abstract»

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  • Magnetic torque properties of imperfectly textured polycrystalline 3 percent Si-Fe with varying amounts of

    Publication Year: 1974 , Page(s): 1052 - 1055
    Cited by:  Papers (2)
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    An equation is presented for the variation of magnetic torque with deviations from ideal View full abstract»

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  • Simple real-time Fourier analyzer and its application to analysis of magnetic torque curves

    Publication Year: 1974 , Page(s): 1056 - 1059
    Cited by:  Papers (2)
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    A method for the simple construction of the discrete Fourier analyzer operating in real time is described. The simplicity is realized by using two basic analog elements, i.e., magnetic analog memory elements and Fourier coefficient calculators using operational amplifiers. Practically, the real-time Fourier analyzer for the calculation of the Fourier coefficients with a scheme of 12 ordinates is constructed. The zero drift of this analyzer is ± 0.1 percent/hour for the full scale. The minimum amplitude of analyzable input signal is about 0.02 in ratio to the maximum amplitude. The maximum sampling frequency is approximately 3 kHz and the minimum sampling frequency has no practical limitation. As an example for its application, the magnetic torque curves are analyzed in on-line real time. The analyzed results almost agree with the results calculated by a general-purpose computer in off-line. This real-time Fourier analyzer is simple and suitable especially for the analysis of the signals changing slowly. View full abstract»

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  • Magnetic bubble logic

    Publication Year: 1974 , Page(s): 1059 - 1066
    Cited by:  Papers (5)  |  Patents (1)
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    Although the literature on the bubble logic devices is limited, the concepts and device configurations are diverse. In conductor-access devices, logic can be performed by bubble transfer operations. In field-access devices, logic can be performed by providing alternative paths which are selected by interaction between bubbles. Examples include the conjugate logic gates, the resident-bubble cellular logic, and the chevron 3-3 circuits. Logic can also be performed by counting bubbles, such as in the symmetric switching function implementation. The various mechanisms for implementing bubble logic are all described by truth tables. To assess their efficiency, they are compared in terms of space and delay when they are used to implement the same logic element - a full adder. They are all comparable except for the resident-bubble cellular logic which requires excessive space and delay. However, it is important to point out that only the symmetric switching function devices offer rewrite-ability to eliminate the part number problem, and accommodation for a large number of inputs to ease interconnection and delay equalization problems. View full abstract»

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  • Fabrication of bubble memory chips

    Publication Year: 1974 , Page(s): 1067 - 1071
    Cited by:  Papers (3)
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    Investigations have been made on the fabrication of accurate and uniform T-bar circuits. Chrome masks are preferable to emulsion masks, and furthermore, a minimum exposure and intimate contact have been demonstrated to be necessary for accurate and uniform pattern imaging on the AZ1350 resist. A newly developed chemical etchant, a nitric acid-base solution without ferric chloride, can almost eliminate undercutting of permalloy elements. Application of spin-on-glass prior to Permalloy evaporation can result in excellent step coverage at the places where T-bar circuits overlap conductors. Large memory chips having a capacity of 16 × 103bits and a storage density of 105bits/cm2have successfully been fabricated. View full abstract»

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  • Bubble cutting circuits

    Publication Year: 1974 , Page(s): 1071 - 1079
    Cited by:  Papers (2)  |  Patents (1)
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    An inhomogeneous applied field can cause an instability in a strip domain that can be used for the controlled generation of bubble domains. These instabilities have been studied experimentally and theoretically by means of a variational calculation. Good agreement is obtained between wall shape calculations and experimental data. Predictions of cutting current as a function of strip width deviate, however, for widths larger than ∼5.5h due to the limitations of the model and the experimental conditions. View full abstract»

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  • Wall placement in a cross-tie memory element

    Publication Year: 1974 , Page(s): 1079 - 1081
    Cited by:  Papers (1)
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    Methods of placing parallel domain walls in magnetic films for a cross-tie memory are described, and a new technique is proposed which involves magnetic annealing at an elevated temperature after the film has been fabricated. View full abstract»

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  • Transient and steady-state velocity of domain walls for a complete range of drive fields

    Publication Year: 1974 , Page(s): 1081 - 1084
    Cited by:  Papers (1)
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    Approximate analytic solutions for transient and steady-state 180° domain-wall motion in bulk magnetic material are obtained from the dynamic torque equations with a Gilbert damping term. The results for the Walker region in which the transient solution approaches the familiar Walker steady-state solution are presented in a slightly new form for completeness. An analytic solution corresponding to larger drive fields predicts an oscillatory motion with an average value of the velocity which decreases with drive field for reasonable values of the damping parameter. These results agree with those obtained by others from a computer solution of the torque equation and those obtained by others with the assumption of a very large anisotropy field. View full abstract»

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  • On the temperature dependence of disturb properties in plated wire

    Publication Year: 1974 , Page(s): 1084 - 1089
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    Theory relating the temperature coefficient of the zero point and digit disturb threshold to the random anisotropy field is discussed. Certain assumptions about the relationship between the random anisotropy of ripple theory and the uniaxial anisotropy field yield relationships that predict the temperature sensitivity of these properties fairly well in Permalloy films. The temperature dependence of most disturb properties appears to be related to the temperature coefficient of the uniaxial anisotropy field from an experimental point of view. Several process variations that can affect the temperature coefficient of the uniaxial anisotropy field are considered. View full abstract»

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  • Quasi-static switching of plated wires in external magnetic fields

    Publication Year: 1974 , Page(s): 1089 - 1091
    Cited by:  Papers (1)
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    Switching thresholds of plated wires were determined with slowly applied external magnetic fields, using both torquemeter and ac techniques. The samples included wires having helical easy-direction angles of 0°, 24°, 30°, and 60°. A study was made of the dependence of switching threshold HCon the angle θ between applied field and wire axis. Good agreement was found with the relation H_{C}(\theta)=H_{C}(0)/\cos \theta for all helical angles and for θ as high as 85°. It is concluded that with the cylindrical film geometry only the axial component of external field is effective in quasi-static switching over wide ranges of field direction and helical angle. View full abstract»

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  • Magnetic hysteresis model

    Publication Year: 1974 , Page(s): 1091 - 1096
    Cited by:  Papers (5)
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    A dynamical model is described which permits calculation of the excitation current I as a function of time in a laminated grain-oriented (G-O) steel transformer core. The independent variable is the magnetic flux density or, equivalently, the coil voltage less the IR drop associated with the resistance R of the windings. Recent observations on flux reversal mechanisms in GO steel indicate that, in the range of magnetic field intensities typically present in transformer cores, the important reversal processes are the motion of long 180° domain walls continuous across grain boundaries and the motion of 90° walls within individual grains. These processes are represented in the model by two subcircuits connected in series. Each subcircuit consists of an inductive element in parallel with a linear resistor which accounts for the eddy current losses accompanying the flux change. The properties of each inductive element (flux vs. current) reflect the two wall motion mechanisms, respectively, in the limit of zero frequency. This model is capable of faithfully simulating minor loop behavior as well as the response to complex waveforms; e.g., the superposition of two or more frequencies. The circuit equations are solved, and some results of computer calculations using a program that implements this model are presented. View full abstract»

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  • Calculation of eddy currents in linear motor geometries--A two-dimensional integral equation approach

    Publication Year: 1974 , Page(s): 1097 - 1099
    Cited by:  Papers (1)
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  • Design considerations of superconducting magnets as a Maglev pad

    Publication Year: 1974 , Page(s): 1099 - 1103
    Cited by:  Papers (1)
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    Design considerations are made on the superconducting magnet as a Maglev pad. The superconducting magnet, called L-type because of its geometry, has two superconducting coils. One is vertically oriented for thrust and guidance, while the other is horizontally oriented for suspension, in one cryostat. The two superconducting coils are both 4 m in length, extremely long in comparison with those that have been constructed so far. Winding techniques of such long coils and structure of a cryostat meeting the contradictory requirements of light weight and solidity are discussed. One of the guiding philosophies of this project was to construct a superconducting magnet with easy operation and simple maintenance, keeping a practical train in mind. In order to meet these requirements, all operating controls, liquid helium inlet valves and current leads were located on the front panel of the cryostat. View full abstract»

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  • Fields in electrical devices containing soft nonlinear magnetic materials

    Publication Year: 1974 , Page(s): 1103 - 1108
    Cited by:  Papers (6)
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    The Colorado method for the solution of the non-linear form of Laplace's, Poisson's, and the diffusion partial differential equations is explained. Various boundary conditions can be satisfied. The transformation of the partial differential equation into a large set of finite difference equations is given. The discretization is based on a grid system consisting of two sets of orthogonal grid lines. The resulting meshes are nonuniform. Successive line overrelaxation method is used for the solution of the nonlinear equations in two steps. For the improvement of convergence, two methods of acceleration of convergence are described. View full abstract»

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  • Nonlinear analysis of the magnetic flux distribution in the magnetized magnet stabilized in air

    Publication Year: 1974 , Page(s): 1109 - 1113
    Cited by:  Papers (4)
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    A theoretical model for the relationship among magnetic quantities describing the one- versus two-dimensional field in a permanent magnet is developed. The model is applied to two problems: 1) determination of the direction of the residual magnetism and 2) finding the magnetic flux distribution in a magnet stabilized in air. The vector potential equation in a form unified for both problems is derived and transformed into a partial-difference algorithm. The numerical line-iteration procedure is described and used to solve these problems for a six-pole permanent magnet rotor of an electrical alternator. View full abstract»

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  • Finite element analysis of the magnetic field distribution inside a rotating ferromagnetic bar

    Publication Year: 1974 , Page(s): 1113 - 1118
    Cited by:  Papers (3)
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    Finite element analysis techniques are being used widely to predict the field distribution in magnetic structures having complex boundary geometries and nonlinear B-H characteristics. In situations where two or more magnetic fields interact, care must be taken to ensure that the principle of superposition applies before adding the fields directly. The magnetic Reynolds number can be used to predict linearity, and in those cases where superposition is invalid, the finite element algorithm must be applied repeatedly in an incremental fashion to ensure accuracy. This procedure is illustrated by considering the magnetic field distribution inside a ferromagnetic bar rotating in a magnetic flux set up by a two pole structure. Results obtained by linearly superposing direct and generated cross axis fields at a particular speed of rotation are compared with the magnetic field distributions resulting from repeated application of the finite element algorithm for incremental step changes in angular velocity. Comparison of the neutral axis angle/speed characteristic for the linear and incremental models shows a significant difference between the two approaches. View full abstract»

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  • A field-theoretical approach to magnetic induction heating of thin circular plates

    Publication Year: 1974 , Page(s): 1118 - 1125
    Cited by:  Papers (5)
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    A field-theoretical approach is used to analyze the subject of magnetic induction heating of thin circular plates by planar coils. Closed-form solutions for the electric and magnetic fields are found to the basic field problem of a single circular loop carrying current at a frequency ω in the presence of a plate characterized by a permeability μ and conductivity σ. By using these fields, expressions are derived for the complex Poynting vector at the surface of the plate, and for the induced EMF in the coil. The theory is extended to include multiturn coils and a field-dependent permeability, and a specific multiturn coil and plate combination is chosen as an example. The complex amplitude of the magnetic field and the Poynting vector are calculated along the surface of the plate using iterative methods to assure self-consistency with the field dependent permeability of the plate. By using Fourier transform techniques, the transient coil current and coil voltage waveforms are calculated under the experimental conditions used to take data on the sample coil and plate. The absorbed power is calculated from these waveforms and is found to be within 10 percent of the measured power absorption for all levels of operation from 50 to 2000 W. The calculated coil current waveform is compared with the measured waveform and is found to be in very good agreement in both shape and period. View full abstract»

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  • Precision code-and voltage-to-resistance converters

    Publication Year: 1974 , Page(s): 1126 - 1129
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    An all-electronic system for automatic setting of the transfer coefficients of operational amplifiers in analog and hybrid computers is described. It is built on the basis of magnetic semiconductor code- and voltage-to-resistance converters. The main features in which the system differs from the conventional types [1] - [3] are the use of internal long-term memory and nonprecision resistors. This results in a reduction of the volume and cost of the converters' hardware. The transfer coefficient setting unit is simplified and high accuracy of conversion is maintained. View full abstract»

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Aims & Scope

IEEE Transactions on Magnetics publishes research in science and technology related to the basic physics and engineering of magnetism, magnetic materials, applied magnetics, magnetic devices, and magnetic data storage.

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Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology